Hydraulic motor or pump



G. A. WAHLMARK HYDRAULIC MOTOR 0R PUMP Feb. 20, 1940.

Filledflay 17, 19:57 4 sheets-sheet 1 Feb. 20, 1940. Q An WAHLMARK 2,190,812

HYDRAULIC MOTOR OR PUMP Filed May 17, 1937 4 Sheets-Sheet F2 Feb. 20, 1940. Q A. WAHLMARK 2,190,812`

HYDRAULIC MOTOR 0R PUMP Filed May 17,. 1937 4 Sheets-Sheet 5 M26? a@ Aga/L Feb. 20, 1940. A WAHLMARK 2,190,812

HYDRAULIC MOTOR OR PUMP Fiied May 17, 19:57 4 sheets-smet 4 Patented Feb. 2.0, 1940 UNITED STATES PATENT oFI-icE z,19o,s1z

HYDRAULIC Moron on PuMr Gunnar A. Wahimark', Rockford, Ill. Application May 17,1937, serial Nc. 143,069

Claims.

The invention relates to a iiuid motor or pump and more particularly to a motor or pump of. the piston and cylinder-type having means for converting the reciprocatory motion of the pistons 5 into rotary motion of a shaft.

A general object of the invention is to providev a device of that character which is of new and improved construction. Y

It is a more particular object to provide a device of that character havingn'ew and improved valve means for controlling the supply and exhaust of iiuid to and from the cylinders of the device.

Another object is to provide in a device of. that character a new form of valvevmeans with the valve thereof having a new motion eiecting a rapid opening and closing of the ports leading to the cylinders without a high speed of the valve as a whole. h FL 5 Yet another object is to provide in a device of the character described a plurality oi annularly arranged ports opening to the cylinders and a valve in the form of a circular plate mounted to have an eccentric movement with respect to the if i ports and in timed relation with thel reciprocation of the pistons.

A further object is to provide in a device of the character described a new and improved means for converting the reciprocatory motion into rotary motion.

Other objects and advantages will becomeapparent from the following detailed description taken in connection` with the accompanying` drawingain which: p y

Fig. l is a longitudinal sectional view taken approximately on line I--I` ofFig. j4 of a pre-` ferred construction embodying the features of the invention.

Fig. 1a is a fragmcniary`deiaii`view-1ckcn apf, proirimately along the line `laf- Ia of Fig.` 1.

Fig. 2 is a transverse sectional view taken ap-` proximately along the line 2-f2 of Fig. 1, partially broken away to revealstructure behind the plane of the iigure.`

i Fig. .3' is'a transverse sectional l"view taken ap- 'prcximatciy aicngtnc lirici-f3 orFig. 1.

Fig. 4 is a ViewA partially in sectionand "par-v` tialiy in elevation takenapproximately along the line 4--4*of"1"lg.l.`V A Fig. 5 is a transverse sectional view taken approximately along the line l-i'lof Fig. 1.`

Fig. 6 is a front elevational view having` in section a modified form of means for varyingthe speed of themoto'rfv i aitncugh tac im/critica is susceptible ci `vaincus modifications and alternative constructions, it is shown herein and Will hereinafter be described in a preferred embodiment and one modication, but it is not intended that the invention is to be limited thereby to the specific construction disclosed, but it is ,intended to cover all modications and alternative constructions falling Within the spirit and scope `of the invention as defined by the lappended claims.

While the principles of construction and operl0 ation oi. the invention are in large part `equally applicable either to a motor or to a pump, these principles, for purposes of disclosure, will hereinafter be described as embodied in a motor. Accordingly, the invention is embodied in a device 15 which comprises generally a casing IIl within which is housed fluid handling mechanism II, which herein is of the reciprosatory type', a rotatably mounted shaft I2 and conversion means I?,` for converting the reciprocatory motion of the iiuid handling mechanism into rotary motion of the shaft. Formed in the casing I0' are a passage I4 anda passage I5 alternatively constituting a passage for the supply of operating uid to the iiuid handling mechanism or a passage for the exhaust of. fluid after its energy has been spent` in .imparting reciprocatory movement to the mechanism depending upon the .direction the shaft I2 isto be rotated.v The supply :and exhaust of operating fluid to and fromthe mechanism is controlledby a valve I6 of unique construction driven bythe shaft I2. L The ,speed ofthe motor, with a constant supply ofu operatingv iiuid,1may be varied by adjustment of the con-` version means I3 either manually by a lever I1 or, automatically 1 by a hydraulic` means ,Iii` (Fig. 6).

In greater particularity, the casing IIJl is com; 4 posed of a plurality of sections 20. 21,2123, and

` 24' secured together as a unit by bgolts 25 cxtc'nd- 4o ing through the sections 24, 23,A A2,2 and`l2ll`and threaded into the section 2|'. Of ithe'seA'lthe'sec` tion 20 constitutes a cylinder block and accordingly has a thick portion 20 formed with a plurality oi'. bores 2 6, herein "7y in number (seme` Fig.4 5), '45

disposed longitudinally of "the casing and annularly arranged. Each ofthe bores constitutes a part of a cylinderof the duid handling mechamsm; V'abutting the fiat faceofzthcscciicn 2u` eter than a b'ore 26. Theserecessesareannularly ISDQSQ and: open through the face or the plate' adjacent the section so that one recess registers with each of the bores 26 to complete the cylinders. Opening to each of. the recesses through the other face of the plate is a port 28 which, as best seen in Fig. 5, is elliptical and is disposed with its major axis tangent to the circle passing through the center of each of the ports. 'I'he cylinder block 20 and the port plate 22 are secured together by means of a shouldered sleeve 29 inserted through a central aperture, formed in the block 20' by a stepped bore 3U, and threaded into the port plate 22.

Reciprocable in each of the bores 26 is a hollow piston 3| connected by means of a piston rod 32 to the motion'conversion means I3. To provide the maximum freedom of movement between the piston 3| and the piston rod 32, the piston rod 32 is connected to the piston 3| by means of a ball and socket joint. Accordingly, the piston rod 32 terminates at its end in a ball 33 which is received within a split socket composed of a divided annular ring 34 and a plug 35. The annular ring 34 rests against a shoulder formed by an internal annular flange 36 formed -in the piston, while the plug is threaded into the' piston to form the head end thereof. The ball and socket joint is well lubricated by means of an oil hole 38 formed in the plug 35, which hole, however, is effectively sealed during the working stroke of the piston by the ball 33 of the piston rod which,` during the working stroke, will bear tightly against the plug 35. i

Section 2| is cup-shaped to complete one end of the casing I0 and to constitute a housing for the conversion means I3. Extending longitudinally of the casing and projecting at lone end through the end of the section 2| is the shaft I2 which derives its rotary motion `from the pistons 3| through the conversion means I3. At its inner end, the shaft is jour-naled in a ball bearing 40 mounted in the bore 30, while at its outer end it is journaled in a ball bearing 4| received in a recess'42 formed in the end of the section 2|. `Both bearings also serve as thrust bearings and to that end the shaft I2 is formed near its inner end with an annular flange 43 which bears against the inner race of the bearing 40 to prevent inward movement of the shaft, and at the point of projection through the section 2| carries a sleeve 44 which is threaded onto the shaft and which is formed with an annular flange 45 bearing against' the inner race of the bearing 4I to prevent out-` ward movement of the shaft. Preferably, a suitable seal 46 is received in an opening 41 through which the shaft I2 projects to prevent leakage outwardly along the shaft. The section 2| is provided with aradially extending flange which may be utilized for mounting the motor.

'I'he conversion means I3 for transforming the reciprocatory motion of the pistons 3| into rotary motion of the shaft I2 herein takes the form of a wobble plate of unique construction. Composing one part of the wobble plate is an inner annular member 52 (see Figs. 1 and 3) encircling l the shaft I2 and pivoted at diametrically opposite points on the ends of a pin 53 extending transversely through an .enlarged and slightly rounded section ofthe shaft I2. Preferably', as best seen y in Figs. 1 and 3, the shaft is iiattened at 54, the

points of projection of the pin 53, and the member 62 likewise is attened in order to aid the pin 53 in retaining the member 52 against rotational movement relative to the shaft I2. Pin bearings 55 are preferably interposed between the ends of the pin 53 and the member 52 in order lthat pivoting of the member with respect to the shaft I2 may encounter little resistance. Near its outer end the member 52 is formed with an'annular groove constituting one race for ball bearings 58 retained in a spacing ring 59, while at its inner end the member is formed with a second annular groove constituting the inner race for ball bearings 60.

Composing another part of the wobble plate is an annular vouter member 64 encircling the inner member 52 and rotatably mounted relative thereto but secured to pivot therewith by means of the bearings 58 and 60 and an' intermediate annular take-up member 65. The member 64 at its outer end is formed with a recess in which is received an outer race 66 for the bearings 58, while the outer race for the bearings 60 is formed by a groove in the take-up member 65. This member is formed at its inner end with threads for engagement with internal threads on the outer member 64 and is disposed to bearl outwardly on the bearings 60 to retain the outer member 64 rotatably on the inner member. It will be apparent that by rotating the member 65 the bearings may initially be adjusted and subsequently any wear in the bearings may be taken up and the member may then be locked in adjusted position by a key 61.

The outer member 64 is operatively associated with the pistons 3| and to that end is formed with a plurality of recesses in its inner face in each of which yis received a semi-spherical liner 1| and To hold the outer member 64 against rotation p while permitting it to wobble freely, a torque arm is provided which here takes the form of a yoke 18, best seen in Fig. 3, which is journaled intermediate its ends on a pin 19 extending downwardly through the top oi the section 2|. Preferably the yoke carries the outer race of ball bearings 8I, the inner race 82 of which is carried by the pin 19. Secured as by a bolt 83 to the outer end oi' each arm of the yoke'18 is an apertured block 84 in which is received a stud 85 extending radially from the member 64 and lat right angles to the pin 19. Encircling each stud 65 is a sleeve 86 formed'with flanges for retaining pin bearings interposed between the block and the sleeve.

With a'conversion means of the character disclosed, the stroke of the pistons 3| and hence the displacement of the motor varies with the tilt of -the wobble plate with respect to the shaft I2. Thestroke and the displacement is zero when the wobble plate is perpendicular to the shaft and increases-as the angle of the plate with a perpendicular to the shaft increases. Thus, by adjusting the tilt of the wobble plate the speed ofthe motor may be varied when the supply of fluid to the motor is constant. Herein the means for adjusting the wobble pl-ate, as best yseen in Figs. 1 and 2, comprises a sleeve 99 encircling the shaft I2 and secured as bya key 9| against rotation relative to the shaft, while permitting longitudinal movement thereof along the shaft. Projecting from the sleeve on diametrically opposite sides arestuds 92 in the same plane as the pin 53 upon which the inner member 52 is journaled. Each stud 92 is connected by a link 93 with a projecting end of a pin 94 extending laterally through a plate 95 welded to the outer face of the inner of the cylinder through which the rod |29 promember 52. The links are retained on the pin and the studs by cotter pinsy 96.

To shift the sleeve 90 longitudinally While permitting rotation thereof with the shaft I2, the sleeve is formed with an annular groove forming one race for ballbearing 91, the other race of which is formed by an annular ring 98 having studs 99 projecting radially on diametrically opposite sides. Carried by each of the studs 99 is a block |00 slidably received ina recess IOI formed in the extremities of a yoke |02 xed on a shaft- |03 extending transversely of the casing I0. The yoke is non-rotatably secured on the shaft by means of a key |04 and functions upon rocking of the shaft |03 to shift the sleeve 90 longitudinally of the shaft I2 which through the links 93 tilts the wobble plate to form a. greater or a lesser angle with the shaft I2. The shaft I 03 is journaled at each end in a sleeve bearing |06 received within a tubular extension |01 projecting laterally from each side of the section 2| near the bottom thereof. Suitable bushings |08 preferably are interposed between the inner end of the sleeve bearing |06 and the yoke |02 and between the tubular extensions |01 and the flanged outer end of the sleeve. At its rear end, the shaft |03 terminates within the sleeve |06 and is concealed by'a cap |09, while at the forward end it projects outwardly of the sleeve. A screw plug IIO threaded through the yoke and into engagement with a recess in the shaft |03 serves to retain the shaft against axial movement relative to the yoke I 02 and relative to the casing. An aperture ||0 is formed in the bottom of the section 2| for giving access to the screw plug IIO.

Herein the shaft |03 maybe rocked to change the speed of the motor either manually kby manipulation of the lever |1 or automatically i through the hydraulic means I8 shown in Fig. 6.

When the shaft |03 is to be rocked manually, lever I1 is secured to the projecting end of the shaft |03 by means of a recessed hub III formed on the end of the lever in which the projecting end of the shaft |03 is received and a pin ||2 extending through the hub and the shaft. The free end of the lever I1 extends upwardly and forwardly into sliding engagement with an arcuate lange II3 formed on a plate I I4 secured on the front side of the section 2|, which flange may carry a scale I|5 for indicating the speed of the motor. Extending loosely through an aperture in the free end of the lever I1 is a pin II6 having a large head II1 for engagement with one side of the arcuate flange |I3, the other side of which is engaged by the lever proper. The outer end of the pin II6 is threaded for the reception of a nut |I8 formed with Spanner wrench holes I I9 by means of which the nut may be tightened rmly to clamp the lever I1 in an adjusted position of the wobble plate resulting in the speed of the motor which is sought.

When the shaft |03 is to be rocked automatically, the plate ||4 is removed from the casing and a plate |25 substituted, which plate carries a cylinder |26 of the hydraulic means I8. Reciprocable in the cylinder is a piston |21 secured by a. pin |23 to a piston rod |29 projecting through rone end of the cylinder |26. At its outer end, the rod |29 terminates in a yoke |30 carrying a pin |3| which is flattened on opposite sides intermediate its ends and at the iiattened portion is received within a slot |32 formed in the free end of an arm |33 secured at its other end as by the pin ||2 to the shaft |03. The end jects is sealed by a packing |34 retained by a cap |35 threaded into a recess |36 in the end of the cylinder.

The head end of the cylinder |26 is closed by a cap |39 having an internally threaded tubular extension |40. Received within the tubular extension |40 and projecting through the cap |39 into the cylinder is an adjusting rod I4I formed with threads |42 intermediate its ends for cooperation with the internal threads of the extension |40 whereby it may be adjusted inwardly or outwardly of the cylinder by rotation. The inner end of the rod I4I extends through a packing |43 retained in a recess |44 formed in the cap |39 by means of an annular ring |45 to prevent leakage of uid along the adjusting rod. Opening to the head endof the cylinder |26 is a port |46 and opening to the rod end is a port |41, whereby actuating fluid may be supplied to the cylinder to shift the piston |21 either to the right or to the left, as viewed in Fig. 6. The

extent of shift to the right is limited by abutment of the yoke |30 with an adjustable stop |48 mounted on the support to which the motor is bolted, and the extent of shift to the left is limited by abutment of the piston with the rod |4I which has a wide range of adjustment. Such shift of the piston to the left rocks the shaft |03 to tilt the wobble plate-in a manner to decrease the speed of the motor; Apertures closed by plugs |48 preferably are provided in the cylinder |26 to permit removal of the pin |28 for disconnecting the piston from the rod I 29. While the hydraulic means` I8 has been described as an alternative means for adjusting the tilt of the wobble plate, it is believed apparent that instead of replacing the plate II4 and the lever I1 with the hydraulic means I 8 the hydraulic means might replace a plate |I4' disposedon the opposite side of the section 2| from the plate II4. The hydraulic means might then be connected to the rear end of the shaft |03 in the manner shown in Fig. 6 and thus provide both a manual and an automatic adjustment in the same construction. i

'I'he left end of the casing I0, as viewed in Figs. 1 and 6, is completed by the sections 23 and 24 with the section 24 taking the form of a cap housing the supply and exhaust passages I4 and I5 which open through the end thereof, and the section 23 taking the form of an annular ring spacing the section 24 from the port plate 22 so as to form a chamber |50 therebetween. The passage generally designated I4 is composed, as best seen in Figs. 1, 4, and 5, of a port I5! which opens into an annular passage |52, in turn communicating with the chamber |50 by. means of a plurality of oblong openings |53 annularly arranged and opening to the chamber |50 at the outermost part thereof. The passage generally designated I5 is composed of a port |54 which opens into a generally circular recess |755 communicating with an annular slot |56 opening through the inner f ace of the section 24. This annular slot |56 is disposed concentric with the shaft I2 and with the ports 23 and is of a smaller diameter than the circle on which the ports 28 are disposed. The circular portion I51of the section 24 severed by the annular slot |56 is retained by means of ribs I58,`as best seen in Figs. 1 and 4,

Disposed in the space between the port plate 22 and the section 24 to control the supply and exhaust of iiuid to and from the cylinders 26 through the passages I4 and I5 is the valve I6.

This valve is adapted to cooperate with the unique arrangement of ports and passages described, and it is of unique construction and has a unique movement whereby opening and closing of the ports 28 in timed relation with the reciprocation of the pistons 3| is effected rvery rapidly, while obtaining a maximum period of port opening during which the fluid is supplied to or exhausted from the cylinders. This rapid opening and closing of the ports is 'effected without a highi speed of the valve asa whole, which is characteristic of rotary valves and which is objectionable and prevents the motor .from attaining high speeds and from operating efliciently at such high speeds. This improved operation is accomplished herein by giving to the valve I6 an eccentric movement with respect to the ports 28 so that opening and closing of the ports `is effected by the eccentric movement of the valve as distinguished from a rotary movement thereof. Accordingly, the valve I6 is circular and is mounted by means of ball bearings, |60 located centrally thereof on a stud I6I formed eccentrcally on the inner end of the shaft I2 and projecting into the space between the port plate 22 yand the section 24.

The faces of' the valve` I6 are ground so as to have a fluid-tight sliding t with the adljacent faces of the port plate -22 and the section 24. The valve is most easily pictured as a wheel having a hub |62 and a rim |63 retained on the hub by a plurality of spokes |64 of reduced thickness so as to form an annular passage |65 opening through both faces of the valve and freely communicating byrmeans of the openings |66 formed between the spokes. This passage |65, as best seen in Fig. 5, is so disposed that it is always in communication with the slot |56 forming a part of the passage I and is of such width that in any position of the valve three of' the ports 28 open in whole or in part thereto. 'I'he rim |63 has a radial thickness which is slightly greater than the width of a port 28 so that in any position of the valve I6, three of the ports 28 are disposed in whole or in part outwardly of the valve I6 to communicate with the chamber |50,

while the seventh port is blocked by the rim |63. It is believed apparent from the foregoing description and Fig. 5 that eccentric movement of the valve I6 as a result of the rotation of shaft` I2 will cause the ports successively to be connec ed alternately with the passage I4 through the chamber |50, and the passage I5 through the annular passage |65 in the valve and the slot f |56. It is believed apparent, moreover, that each port 28 will be closed when the piston 3| is at its dead center point, namely, when reversing from a power stroke to an exhaust stroke and from an exhaust to a power stroke, and that the opening or closing o'f a port will be very rapid because, as clearly seen in Fig. 5, in the position of the valve shown and the position of the stud I6I the valve has a large movement in a vertical direction thereby rapidly closing and opening the ports at the top of the figure and at the bottom of the figure, while it has practically no movement in a horizontal direction, thereby leaving the ports at the side of the figure wide open and in communication with the chamber |50 andthe passage |65 respectively.

While the passages I4 and I5 may alternately serve as supply or exhaust passages depending upon the direction which the shaft |2 is to be rotated, if it be assumed that the shaft is to be rotated in a clockwise direction, as viewed in Figs.

supply passage whereas the passage `|5 will constitute the exhaust passage. The operation of the motor briefly will then ber as follows: Assuming that the valve is in the position shown, the operating fluid' supplied through the passage |4 will enter the chamber |50 through the openings |53 and will flow through the three ports to the left of the valve I6, as viewed in Fig. 5, and will impart a working stroke to the pistons 3| in the cylinders with which those ports communicate. As a result, the wobble plate will be actuated and the shaft I2 rotated in a clockwise direction, as viewed in Fig.` 5. With an actuation of the wobble plate and the shaft, three of' the pistons willl be moved through an exhaust stroke and the uid from the cylinders in which those pistons reciprocate will be discharged through the three ports shown in the right half of Fig. 5, which ports are inwhole or in part open to thepassage |65 ofthe valve I6. 'Ihe exhaust fluid will flow through the openings |66 between the spokes of the valve' and thence out through the ,annular slot |56, recess |55 and port |54. The seventh and topmost piston, shown in Fig. 1, is just reversing from an exhaust to a power stroke and correspondingly the port 28 thereof is closed by therim |63 of the valve as it is moving to change the connection of the port from the passage |65 to the chamber |50. It will be apparent that as the valve is eccentrically driven in a clockwise direction, as viewed in Fig. 5, the uppermost port 28 will be uncovered and connected to the chamber |50 so that operating fluid may be supplied thereto and impart a working stroke to the piston, and that as the valve is further moved each of the ports will successively be connected to the chamber |50 to receive operating fluid, blocked while the respective piston is reversing from movement in one direction to movement inr the other, then opened to the passage |65 in the valve to permit discharge of the exhaust fluid, and is then again blocked while the piston again is reversing and the cycle.

It is believed apparent from the foregoing that I havev perfected a motor or pump which has many novel and advantageous features, among the most important of which is the novel valve means which I have disclosed, and the novel construction of the wobble plate and the torque fbination, a casing having a plurality of cylinders formed therein and a cylindrical valve chamber having parallel end faces, a port opening to th'.. head end of each cylinder and to one end face of said valve chamber in an annular row, a fluid passage opening to said valve chamber radially outwardly of said ports and a second fluid passage opening to said valve chamber radially inwardly of said ports, valve means operable successively to connect said ports alternately to the passage opening radially outwardly of the ports and to the passage opening radially inwardly of said ports, said valve means comprising a wheel-like member having a hub, a rim,

and spokes connecting the rim to the hub to provide a passage from one face of the Wheel to the other which is sealed about its inner periphery by the hub and about its outer periphery by the rim, said hub having end faces of substantially equal area in fluidftight sliding engagement with the end faces of said valve chamber and said rim to each of the cylinders, said ports beingan- .nularly arranged, a section having fluid supply and exhaust passages formed therein and having a hat face disposed opposite the ilat face of said cylinder block, and an annular spacer interposed between said section and' said cylinder block and cooperating with said cylinder block and said section to form a cylindrical valve chamber, one of said passages in said section communicating with the valve chamber inwardly of said ports, and the other of said passages communicating with said valve chamber adjacent the periphery of the valve chamber, and an integralwheel-like valve having a hub and a rimy each having a fluid-tight sliding t with the :face of both said cylinder block and said section, and spokes of reduced thickness connecting said hub and said rim to provide an annular passage opening through each face of the valve, said passage always being in communication with the passage in said section opening to the valve chamber inwardly of said ports, and the valve chamber beyond the rim of the valve always being in comy munication with the other of said fluid passages in said section. and means for imparting to said valve an eccentric motion whereby the valve successively connects said ports .alternately to the supply and exhaustpassages in said section. p

motor block faces, iluid supply and exhaust passages, one of said Vpassages communicating with the space formed betweerrsaid motor block and said section inwardly of said ports and the other of said passages communicating with said space jadjacent the periphery of the space, and a wheellike valve having a rim and a hub each having section, and means for imparting to said valve an eccentric motion whereby the valve successively connects the ports alternately to' the sup` ply and exhaust passages.

4. In a device of the character described, a casing having a plurality of annularly arranged cylinders formed therein and a cylindrical valve chamber adjacent one end of said cylinders having parallel end faces, a port opening to eachof said cylinders and to one end face of said valve chamber, and uid supply and return passages,

one opening to said valve chamber radially outcentrically of said annularly arranged cylinders,

means for converting the reciprocatory motion of said pistons into rotary motion of said shaft,

and a wheel-like valve positioned in said valve chamber controlling the supply and exhaust of iluid to and from said cylinders having a rim and a hub each having end faces in fluid-tight sliding engagement with the end faces of said valve chamber, and a stud mounted eccentrically on the inner end of said shaft and engaging said valve centrally th'ereof to drive the same through an eccentric motion in timed relation with the reciprocation of said pistons.

5. In a device of the character described, a casing comprising a motor block having a plu'- rality of annularly arranged parallel cylinders formed therein and a port opening through one face of the lbloclr to each of the cylinders, said ports beingV annularly arranged, a section having fluid supply and exhaust passages formed therein and an annular spacer interposed between said section and said motor blockand cooperating therewith to form a cylindrical valve chamber, one of said passages communicating with saidjvalve chamber inwardly of said ports and radially outwardly of the center of the chamber, and the other of said passages communicating with said chamber adjacent the periphery of the chamber, and a wheel-like valve comprising a rim, 'a hub and connecting spokes, said rim and hubeach having a iluid-tight sliding ilt in said valve chamber with both said motor block and said section, said hub and rim providing said valve with a fluid-tight seal 'at its inner periphery as well as at its outer periphery, and means for imparting to said valvey an eccentric motion whereby thevalve successively connects the ports alternatelyv'tothe supply and` exhaust passages.

l Gorman. s. wAnrMAnK. 

